Conventionally, a vehicle such as an automobile includes a heat exchanging device for exchanging heat with an internal combustion engine, which is a motor, to cool the engine and an air conditioning device for heating the interior of the passenger compartment using the heat transmitted from the engine to the heat exchanging device.
The heat exchanging device circulates heat exchanging fluid in a circulation path passing through the engine and thus causes heat exchange between the fluid and the engine. When heated to a high temperature, the engine is cooled through such heat exchange between the heat exchanging fluid and the engine. The air conditioning device has a blower driven to discharge warm air into the passenger compartment. When the blower is activated, the air is passed through a heat exchanger on the circulation path in the heat exchanging device. This causes heat exchange between the air and the heat exchanging fluid. The heated air is then sent into the passenger compartment. That is, as the blower is activated in response to a request for heating, a flow of air is generated to pass air through the heat exchanger. The air is thus heated by the heat exchanging fluid and then directed into the passenger compartment, thus heating the interior of the passenger compartment.
When the engine is started from a cold state, the temperature of the heat exchanging fluid in the circulation path of the heat exchanging device is low in the period immediately after the engine starts. Accordingly, even though the blower is activated to direct the air through the heat exchanger in response to the request for heating, the air cannot be effectively heated by the heat exchanging fluid. As a result, even if the air is provided to the passenger compartment after having passed through the heat exchanger, the air cannot heat the interior of the passenger compartment. In this state, occupants may feel cold, and thus the comfort level in the passenger compartment is lowered.
To solve this problem, as disclosed in Patent Document 1, it has been proposed to mount a seat heater heated by a heat source other than the engine, which is, for example, an electrothermal type seat heater that generates heat using electrical power supplied to the seat heater. When the temperature of the heat exchanging fluid in the circulation path is low, the blower of the air conditioning device is not activated even if heating is requested, and the occupants are warmed by means of the seat heater. In this case, even when cold heat exchanging fluid in the circulation path prevents the air conditioning device (the blower) from directing warm air into the passenger compartment, the seat heater warms the occupants and provides heat in the passenger compartment. The comfort level in the passenger compartment is thus prevented from being lowered.
If the temperature of the engine rises and thus the temperature of the heat exchanging fluid in the circulation path, which receives heat from the engine, increases to such a level that the heat exchanging fluid can be used to heat the interior of the passenger compartment, the blower of the air conditioning device is actuated to direct warm air into the passenger compartment, thus heating the interior of the passenger compartment. In contrast, supply of power to the seat heater is stopped. As has been described, by selectively stopping and operating the blower and selectively permitting and prohibiting the power supply to the seat heater, the occupants are warmed in response to a request for heating without unnecessary actuation of the blower or unnecessary heat generation by the seat heater.
Recent vehicles exhibit improved engine thermal efficiency, which is brought about by reducing the size of the engine and ensuring automatic stopping and re-starting of the engine. In other words, heat generated by an engine is decreased. Accordingly, additional components of the vehicle must be heated when at a cold temperature, aside from the passenger compartment.
For example, a catalyst is mounted in the exhaust system of an engine mounted in a vehicle to purify exhaust gas. To ensure maximum catalyst performance for purification of the exhaust gas, the catalyst must be completely warmed up by raising the catalyst bed temperature, which is the temperature of the catalyst, to an activation level at which the catalyst is activated. However, the above-described vehicles in which the engine generates less heat tend to have a low temperature for engine exhaust gas. As a result, at certain outside air temperatures and in certain operating states of the engine, it may be impossible to raise the catalyst bed temperature to a value greater than or equal to the activation level, or, in other words, to complete warm-up of the catalyst.
Also, the transmission is connected to the output shaft of the engine of the vehicle. Rotation of the engine is thus transmitted to wheels of the vehicle through the transmission. The transmission uses transmission oil. When the temperature of the transmission oil reaches a level that is high to a certain extent (which is, for example, the temperature t1) with respect to normal temperature at the time when the engine is not running, the transmission is allowed to achieve such an operating state that the fuel consumption of the engine decreases. Accordingly, to reduce the fuel consumption, it is contemplated to cause heat exchange between the heat exchanging fluid in the circulation path in the heat exchanging device, which is mounted in the vehicle, and the transmission oil, thus maintaining the temperature of the transmission oil at a level higher than or equal to the temperature t1. However, in the above-described vehicles in which the engine generates less heat, the heat exchanging fluid, which is heated through heat exchange with the engine, tends to exhibit a low temperature. As a result, at certain outside air temperatures and in certain engine operating states, it may be impossible to increase the temperature of the transmission oil to a value greater than or equal to the temperature t1.
Additionally, the engine mounted in a vehicle uses lubricant oil. When the temperature of the lubricant oil reaches a value that is high to a certain extent (which is, for example, the temperature t2) with respect to a normal temperature at the time when the engine is not running, the viscosity of the lubricant oil decreases and the resistance of the lubricant oil against rotation of the engine reduces. The lubricant oil thus achieves such a state that is effective to decrease the fuel consumption. Accordingly, to reduce the fuel consumption, it is contemplated to cause heat exchange between the heat exchanging fluid in the circulation path in the heat exchanging device, which is mounted in the vehicle, and the lubricant oil, thus maintaining the temperature of the lubricant oil at a level higher than or equal to the temperature t2. However, in the above-described vehicles in which the engine generates less heat, the heat exchanging fluid, which is heated through heat exchange with the engine, tends to exhibit a low temperature. As a result, at certain outside air temperatures and in certain engine operating states, it may be impossible to increase the temperature of the lubricant oil to a value greater than or equal to the temperature t2.
That is, in the above-described vehicles, the catalyst mounted in the exhaust system of the engine, the transmission oil used in the transmission, and the lubricant oil used in the engine correspond to the components aside from the passenger compartment that must be heated when at a cold temperature.
If the technique of Patent Document 1 is used in these vehicles, the heat produced by the engine is distributed preferentially to the passenger compartment but not to the components of the vehicle aside from the passenger compartment that must be heated when at a cold temperature. Specifically, when heating is requested and the heat generated by the engine increases the temperature of the heat exchanging fluid to such a high level that the heat exchanging fluid may be used to heat the passenger compartment, the blower of the air conditioning device is actuated to discharge the air heated by the engine as a heat source into the passenger compartment. In other words, the heat produced by the engine is distributed preferentially to the passenger compartment by means of the heat exchanging fluid and the air. This makes it difficult to provide the heat generated by the engine to the components aside from the passenger compartment that must be heated when at a cold temperature, which are the catalyst, the transmission oil, and the lubricant oil.
If the heat of the engine is not distributed preferentially to the components aside from the passenger compartment that must be heated when at a cold temperature, including the catalyst, the transmission oil, and the lubricant oil, the temperatures of these components decrease, thus preventing the engine from reducing fuel consumption and improving exhaust emission.
Patent Document 1
Japanese Laid-Open Utility Model Publication No. 5-18909 (paragraphs [0032] to [0036])